CSS Paper Botany 2013 MCQs

Animals are heterotrophic, meaning they obtain their energy and nutrients by consuming other organisms or organic matter. Unlike plants, which are autotrophic and produce their own food via photosynthesis, animals must ingest external sources of carbon and energy to survive and grow.

Robert H. Whittaker proposed the five-kingdom classification system in 1969. This system categorized living organisms into Monera, Protista, Fungi, Plantae, and Animalia based on cell structure, mode of nutrition, and body organization. It became a standard framework in biology for many years, significantly improving upon earlier two-kingdom systems.

Botany, also known as plant science or plant biology, is the branch of biology that focuses on the scientific study of plants. This field encompasses the investigation of plant structure, properties, biochemical processes, classification, and their ecological interactions with the environment, distinguishing it from zoology, which focuses on animals.

The term 'spike moss' is the common name for members of the genus Selaginella, which falls under the class Lycopsida. They are called spike mosses because they produce strobili that resemble spikes and have a moss-like appearance, despite being vascular plants.

The genus Selaginella is the sole living genus within the family Selaginellaceae. While it belongs to the order Selaginellales and the class Lycopsida, the specific family classification for this genus is Selaginellaceae.

In the development of the microspore in Selaginella, the primary androgonial cells undergo repeated mitotic divisions to form a mass of androcytes. These androcytes eventually metamorphose into biflagellate or multiflagellate antherozoids (sperms) which are released for fertilization.

In many plant stems, the hypodermis is the layer situated immediately below the epidermis. In species like Selaginella, this region is often differentiated into sclerenchymatous cells, which provide mechanical support and structural integrity to the stem, protecting the inner tissues from physical stress.

The stele in the Selaginella stem is often suspended in a large air space within the cortex. This space is bridged by elongated, radially arranged endodermal cells known as trabeculae. These cells provide structural support to the central vascular cylinder while allowing for gas exchange.

The rhizophore is a unique, specialized, leafless, cylindrical structure found in many species of Selaginella. It arises from the stem at the point of branching and grows downward into the soil, where it produces adventitious roots upon contact with the substrate.

In Selaginella, the leaves that are associated with sporangia are specialized and referred to as sporophylls. These sporophylls are often arranged in a compact structure known as a strobilus or spike at the tips of the branches. The sporangia are located in the axils of these modified leaves, which serve to protect and support the developing reproductive structures.